Jewelweed - species profile

 
What: With my last post on poison ivy, I wanted to return to another good friend of mine: jewelweed (Impatiens capensis). In Centennial Woods, we only have spotted jewelweed (the yellow-flowered pale touch-me-not is found on much richer sites). I spent some time observing it while watching the hummingbirds, admiring its simple elegance. The flowers are so rich and ornate, with no shortage of suitors begging nectar. It grows abundantly anywhere there's water so I headed down into Centennial Woods below the sandy slopes and found a great patch to take some photos.

Ecological notes: Much like raspberry stems and boxelder twigs, the stalks of jewelweed have a weird white powdery bloom to them. I still have no idea what the function of these is, so if anyone knows, send me an email! I was told that it was yeast, but some sources say that this is just a myth wine makers false propagated. I would assume it might then have something to do with resistance to predation by insects or maybe it's a fungicide or for preventing water loss? Researchers in Osaka found that the bloom, at least on grapes, is oleanolic acid. They link it to preventing dehydration. Since jewelweed grows in intermittently wet areas, the bloom could prevent the plant from losing water in droughts (like right now) and thus maintain the stem's rigidity. Sounds reasonable. But why would boxelder twigs have the bloom?

Minute hairs on the surface of the leaves trap air and cause water to bead on the surface. When you hold a jewelweed leaf underwater it seems to transform miraculously into silver! These leaves were holding some of that much needed rain from last night. Many other plants do this too, and since it's a pattern we have to have a super cool esoteric word for it: superhydrophobicity (really afraid of water!! aka the lotus effect). Some plants achieve superhydrophobicity by having a dense coating of bristly hairs, others, like lotus, have waxy cuticles. Supposedly this is linked with both water retention as well as being able to wash leaves clean, even with dew. Since the water beads up it has a high internal charge and will pull dust and other stuff off the leaf surface. 

Yesterday I was noting that many had the malformed flowers, or galls. Inside that green blob there's a Jewelweed gall midge (Schizomyia impatientis). They hatch early fall and overwinter as adults. 

Where: There's a great patch of the spotted kind in CW where an intermittent stream drains off the slope (it's been dry most of the summer though) and you can follow the flow of the water by where the jewelweed grows. Jewelweed definitely prefers wetter areas. So when you find poison ivy, often times walking downslope or finding a drainage will yield a good patch of jewelweed.

Other notes: Jewelweed is pretty easy to cultivate. It's herbaceous, so it dies back every year, but it has perennial roots so it shoots up from the same spot each year. The seeds are spring loaded so when you touch them they erupt out from the pod (see the image of a swollen pod above). They're just now ripening. Seeds taste like walnuts and they've got about 3-5 per pod. Because they shoot so far they'll easily colonize a nice little patch. Ask Zac to see his jewelweed garden started from a single plant!

Poison ivy

What: Above is an amalgamation of 23 photos I took of poison ivy leaves (the three leaves are actually leaflets and collectively form a single leaf). I then put the transparency of each image at 1/23 to get the final result. I got the idea from visual artist Jason Salavon. I've been really interested in the diversity within a species, particularly since everything at this time of year is so abundant. It started with toads (will post a series of photos of them) but turned to poison ivy.

Yesterday I was out with my UVM class, Natural History of Centennial Woods, and we were taking a closer look at poison ivy (Toxicodendron radicans). I'm not a big fan of the "leaves of three let it be" mantra as it prevents people from actually looking at the plant. Besides, strawberries have 3 leaves, as do boxelder, clovers, some Virginia creeper, sarsaparilla, and heaps of other delicious and beautiful plants.

To avoid confusion and cement an understanding of what poison ivy looks like, we created a list of features that would help us distinguish it from other plants. Here are some of the ones I can remember:

• Woody stem
• Three leaves
• Often has toothed edges to leaflets, rarely smooth (or entire)
• Fades to a dull yellow 
• Vines have "hairs" on them (see image below)
• Middle leaflet has longer petiole (what attaches leaflet to stem) than two side leaflets
• Middle leaflet symmetrical, lateral ones asymmetrical
• Two leaflets on side look like they're giving the thumbs down

Ecological notes: Also of note on the poison ivy leaves were an abundance of poison ivy leafminers (Cameraria guttifinitella) that appear to be eating the upper layer of cells on the leaves. A couple years ago I watched a catbird eat the berries from poison ivy with great relish. I've seen rabbits nibble leaves, and apparently plenty of other animals will eat the plant and be unaffected by urushiol, the toxic oil in the leaves, stem, and buds that cause us such great irritation. So just because you see an animal eat something doesn't mean you can (particularly don't try and learn which mushrooms to eat by watching red squirrels).

Where: Centennial Woods, and any moderately rich, well-drained but moist soil near you.

Hummingbirds

Female ruby-throated hummingbird (note white tips on tail)

Visiting purple loosestrife

What: The second half of the last post is a delightfully little bundle of energy! Ryan and I had headed down to the powerlines after Jon told us about how many hummingbirds there were. I have been waiting for the spotted jewelweed (Impatiens capensis) to blossom, as each summer around mid/late August we get a flush of ruby-throated hummingbirds (Archilochus colubris) feeding on the nectar.

Ecological notes: Any hummingbird gardening guide lists jewelweed as a must (apparently ruby throated hummingbirds prefer spotted jewelweed to yellow jewelweed, I. pallida). Bumblebees and some butterflies also visit jewelweed flowers, but they're not nearly as effective at pollinating the plant, indicating that an evolutionary relationship might exist between the morphology of the flower and the feeding behavior of hummingbirds. I found some interesting notes about the relationship between the two, with unsupported claims that the weak petiole of the flower allows the plant to bend away from the hummingbird's advances, thus protecting the plant's ovaries from the long sharp piercing bill of the bird. Problem is that the complex shape of the flower places the ovaries at the back of the flower, well out of reach of the bird.

Research out of UMass Amherst indicate another, more likely possibility. Jewelweed flowers have flexible pedicels (stems) that allow the flower to bend readily. When feeding, hummingbirds flick out their tongue to slurp out the nectar. Each time the bird does so the weak pedicel allows the flower to recoil back in response and before flapping back forward. As it springs forward the flower dusts its pollen across the upper bill of the bird. It all happens in a brief second, so it's difficult to observe, but the tight relationship is enough to ensure successful pollination. To test this relationship, the researchers immobilized some flowers by wrapping wire around their pedicels. The rigid flowers were far easier for the hummingbirds to suck nectar from (visits were 25% shorter to these flowers), but significantly decreased pollen transfer (by about 50%). They also found that the stems of the flower didn't move when visited by bees, indicating that this is indeed an adaptation specific to hummingbird foraging behavior.

According to the researchers, there may also be a link between the shape/size of the spur (the hook at the back of the flower) and which pollinators (bees vs. birds) go after the individual flower.

Where: Centennial Woods, powerline

Other notes: Summer is coming to an end - you can feel the first crisp coolness of the night air. Queen Anne's lace is going to seed, morning glories and bind weed flowers are out in full force, fruits are ripening (go harvest wild grapes!), Jerusalem artichoke is flowering, and the birds are getting antsy ready to head south.

Dew this morning

What: Ryan and I went on a Centennial Woods wander early this morning right as the sun was coming over the Greens. The grass soaked our feet, and everything under the powerlines was covered with dew; a steamy mist was rising up from the ground and the forest had a beautiful glow.

Ecological notes: We had really warm weather yesterday (in the 80s, and an afternoon rainshower) and it was relatively warm at night, cooling significantly by about 4am. Dew forms when heat radiates off an object and moisture in the air condenses out as it cools (like when droplets form on a cool glass of lemonade). The rate of condensation has to be quicker than rate of evaporation. So you wouldn't expect to get dew when:

• it's windy (increased rate of evaporation), 
• dry (not enough moisture to condense out), 
• there's little difference in temperature between the surface of an object and the air
• when it's super sunny or when it's cloudy

This is why dew tends to form in the morning or evening under a cloudless sky without wind. Dew is a common late summer phenomenon when days are warm and nights cool. But because the ground is so warm in the late summer, things directly touching the ground don't have dew on them. On the other hand,leaves, my windshield, and other exposed surfaces do get dew.

Where: Centennial Woods

Other notes: The jewelweed is in full bloom right now, providing some wonderful late season nourishment for bees and hummingbirds.

Harvesting Honey

What: Callan, Zac, and I suited up and checked in on our hives. A few weeks ago we added supers to the hives and were hoping that the time for harvesting was finally here. And indeed it was! We gave one of our hives a headstart by giving it drawn out comes at the beginning of the season, and the upper of its two supers was completely drawn out with capped honey and no brood. The super probably weighed upwards of 30 pounds! The video shows a bit about the harvesting process once the frames had been removed from the hive. Zac also shows off some wonderful natural history knowledge.

It was amazing to see how much honey we harvested relative to the size of the super. The ball jars are actually sitting on a deep, which is 9 5/8" deep, whereas the super we harvested from is only 6 5/8" deep (its total volume is only about 1.2 square feet). 

Ecological notes: A lot of the clovers are past their peak and the mints, late season squash flowers, and goldenrods are taking center stage. I've seen the first knotweed flower buds, which is among the last sources of nectar for honey bees before winter sets in.

Where: My backyard

Other notes: We got about 2.5 gallons of honey off of our first harvest. Last year we had an early and a late harvest off of one hive, totally about 5 gallons of honey. Hopefully we will be able to harvest honey from our other two hives this year if we get a good flush of nectar over the next few weeks.